Electrical discharge device



June 13, 1944. H. H. RACE ELECTRICAL DIS CHRGE DEVI CE Filed May 15, 1942 Inventor-z Hubert H. Race,

` AttoT-n ey.

Patented June 13, 1944 ELECTRICAL DISCHARGE DEVICE Hubert H. Race, Schenectady, N. Y., assigner to General Electric Company, a corporation of New York Application May is, 1942, serial No. 443,059

4 Claims.

My invention relates to spark plugs and similar electrical discharge devices.

An object of my invention is to provide an improved'spark plug unit having a construction which minimizes the possibility of electrical ilashover within the plug by substantially eliminating gas electrical discharge paths between the connection formed between the distribution lead and the grounding shell of the plug.

` Further objects and advantages of my invention will become apparent and my invention will be better understood from the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In the drawing Fig. l is an elevational view, partly in section, of a spark plug and a distribution lead illustrating an embodiment of my invention; and Fig. 2 is an enlarged sectional view of the lead and plug adjacent the connection of the lead to the plug electrode.

Referringto the drawing, I have shown a spark plug provided with an outer metallic sleeve or barrel I0 threaded at one end II for engagement with a complementary threaded opening in an engine block and having an enlarged shoulder portion I2 adapted to be engaged by a wrench or similar tool. Grounding electrodes I3 are secured to the shell I adjacent the lower threaded end Il, and a central or discharge electrode I4 is supported within the spark plug by a ceramic insulating core I5 of porcelain or similar material. The discharge electrode I4 is provided with a lower ange or shoulder I5 which engages a complementary shoulder II on the insulating core l5 and is provided with a turnedover contact head portion I8 which secures a cap I9 in position over a central opening 2l in the insulating core I5. 'I'his central opening 20 in the core I5 between the flange l5 and the cap I9 is filled with a body of compressed or compacted powder 2|. The core I5 is held in position in the shell In by engagement adjacent its lower end with a gasket 22 seated on a shoulder 23 formed on the shell III and by engagement at the opposite end thereof with the turned over end 24 of the shell III.

'I'he desired electrical potential is brought to the central electrode I4 by a distribution lead 25 of electrically conductive material which is insulated by a suitable flexible insulating covering 26 about which an armored metallic shield 2l is arranged. The distribution lead is secured to the spark plug by a terminal elbow 23 which is secured to the head oi' the spark plug shell Il by a nut 25 which threadedly engages a threaded upper end portion on the spark plug shell III. The nut 29 is provided with an annular ange 3| extending over a complementary ilange 32 of the elbow 28 and secures the elbow ilange 32 against a heat resistant bushing 33 of deformable resilient material, such as the composition described in British Patent 513,630 (1939) which is arranged between the flange 32 and the 'upper end 24 of the shell I0. In order to assure good electrical contact between the spark plug central electrode I4 and the distribution lead 25, a terminal connector is provided which includes an electrically conductive bushing 34 having a central passage 35 therein through which an end of the distribution lead 25 extends. This bushing is held in position in an insulating sleeve element 35 of relatively non-deformable material, such as Textolite, porcelain or mycalex, and is securely anchored thereto by an annular flange 3'I which extends into a complementary groove formed on the outer peripheral surface of the bushing 34. A Contact comprising a coil spring 38 is arranged over the end of the bushing 34 and extends from the adjacent end of the insulating sleeve 36 into contact with the upper end of the central discharge electrode I4.

Under certain atmospheric conditions, such as relatively low pressure, there is a tendency for the voltage to discharge from the lead 25 to the grounded plug shell I0 through any gas discharge path which may exist Within the shell. In order to eliminate corona and electrical arc-over discharges between the spark plug shell I0 and the electrical connection of the distribution lead 25 with the central electrode I4, I-provide a heat resistant bushing 39 of deformable resilient insulating material similar to bushing 33 arranged within the shell between the end 24 of the shell and the electrical connection of the lead 25 with the discharge electrode I4. This deformable bushing 39 is pressed into deformed position by engagementof the lower end of the terminal member insulating sleeve 36 with the upper edge of the resilient bushing 23 for substantially nlling a circumferential portion of the space about the lead connection and sealing the space between the lower end of the terminal member and the shell, thereby substantially eliminating free open gas electrical discharge paths between the lead and electrode connection and the shell around the outside of the terminal sleeve member 33. When this bushing is deformed in this manner, a part of the upper portion thereof extends upwardly around the insulating sleeve 36 about the lead -25 and seals the air space between the lead connection and a portion of the upper resilient bushing 3i which extends between the insulating sleeve 36 and the upper end 24 of the grounded shell I Il, thereby further minimizing the tendency towards corona and arc-over discharges through vthe air space between the lead connection and the upper end of the shell. The

two bushings 33 and 39 are securely held in their deformed positions by tightening the nut 29 on the upper end of the shell I0, as.this biases the elbow 28 into tight engagement with the upper portion of the bushing 33 and with the upper end of the insulating sleeve 36, thereby biasing the sleeve into tight engagement with a portion of the upper end of the bushing 39. Under member 36. I minimize the possibility of such A discharges by providing a substantially conical or tapered portion l on the end of the distribution lead insulation 26 and arranging this tapered portion 40 in engagement with a complemenf tary portion 4Iy of a heat resistant bushing 42 of deformable resilient insulating material similar to bushings 33 and 39. A tight engagement between the complementary surfaces of the tapered portion 40 and the bushing 42 is obtained by drawing the end of the distribution lead 25 through the opening 35 in the electrically conductive bushing 34 and securing the end of the lead 25 tothe end of the bushing 34. asby soldering. 'Ihis provides a sealed chamber about the connection of the distribution lead 25 to the discharge electrode I4 and eiectively seals in the air or other gas within the chamber arranged about this electrical connection, thereby eliminating all free open gas electrical discharge paths between the grounded shell i0 and the connection between the lead 25 andthe electrode i4.

While I have illustrated and described a particular embodiment of my invention, modications thereof will occur to those skilled in the art. I desire it to be understood, therefore, that my invention is not to be limited to the particular arrangement disclosed. and I intend in the appended claims to cover all modifications which do notI depart from the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A; spark plug including a shell having a grounding electrode, a discharge electrode arranged within said shell, means includingfan insulating element arranged about a part of said with said deformable bushing deforming said= bushing for substantially filling a portion of .the

space about said lead-connection for providing a seal thereabout-with said insulating member and around said non-deformable insulating element, and means about said lead within said non-deformable insulating element between said shell 'and the connection of said lead to said elec,

trode providing a sealed space withinsaid shell about said connection `for eliminating free open gas electrical discharge paths and said connection.

2. A spark plug including a shell having a grounding electrode, a discharge electrode arranged withln said shell. means including an between said shell insulating element arranged about a part of said element arranged about said lead in engagement with said deformable bushing deforrning said bushing for substantially lling a portion of the space about said lead'connection for providing a seal thereabout with said insulating element and around said non-deformableinsulating element; and means including a heat resistant bushing about said' lead within said non-deformable insulating element between 'said shell and the connection of said lead to said electrode providing a sealed space within said shell about said connection for eliminating free open gas electrical discharge paths between said shell and said connection. l,

3. A spark plug including ajshell having a grounding electrode, a discharge electrode arranged within said shell, means including an insulating element arranged about a part of said discharge electrode in said shell for supporting said electrode, a -distribution lead, means for connecting said lead to said discharge electrode within said shell, aheat resistant bushing of deformable resilient insulating material arranged between said shell and said electrical connection of said lead to said discharge electrode, means including a relatively non-deformable insulating element arranged about said lead in engagement with.

' an'd the connection of said lead to said electrode providing a sealed space within said shell about said connection for eliminating free open gas electrical discharge paths between said shell and said connection.

4.1A spark plug including a shell having. a. grounding electrode, a discharge electrode arranged within said shell, a distribution lead, means forconnecting said lead to said discharge electrode within said shell, a heat resistant bushing of deformable resilient insulating material arranged between said shell and said electrical connection of said lead to .said discharge elec-V trode, means including'a relatively non-deformable insulating element arranged about said lead in engagement with said deformable bushing deforming said bushing for substantially lling a-portion of the space about said lead connection for eliminating free open gas electrical discharge paths between said lead and said shell around saidnon-deformable insulating element, and

means including a heat resistant bushing of deformable resilient insulating material arranged about said lead within said non-deformable insulating element between said shell and the connection of said lead to said electrode providing a sealed space within-.said shell about said connection for eliminating free open gas electrical discharge paths between said shell and said cony nection.

HUBERT H. RACE. 

